1. Field of the Invention
The present invention relates to a semiconductor element and a method for producing the semiconductor element, specifically, to a semiconductor element configured to absorb infrared light and a method for producing the semiconductor element.
2. Description of the Related Art
Infrared light ranging from the near-infrared region to the mid-infrared region corresponds to the absorption spectrum region relating to the environment and living bodies including animals and plants. Developments of photodetectors for such wavelength regions are underway. The developments are mainly directed to photodiodes having absorption layers containing III-V compound semiconductors. The developments each put emphasis on the production of an epitaxial wafer having high crystallinity for the purpose of suppressing dark current. For example, Japanese Unexamined Patent Application Publication No. 2011-054915 discloses an embodiment directed to the near-infrared region and including growth of an epitaxial layered body including an absorption layer having a type-II III-V compound semiconductor (InGaAs/GaAsSb) multiple quantum well (MQW) structure by metal-organic vapor phase epitaxy using only metal-organic sources (all metal-organic source MOVPE). Japanese Unexamined Patent Application Publication No. 2012-009777 discloses an embodiment directed to the mid-infrared region and including formation of an absorption layer having an InAs/GaSb multiple quantum well on a GaSb substrate particularly by molecular beam epitaxy (MBE). This document states that an InSb strain-compensating layer, which is not employed therein, may be employed for strain compensation. X. B. Zhang, et al. “Metalorganic chemical vapor deposition growth of high-quality InAs/GaSb type II superlattices on (001) GaAs substrates”, Applied Physics Letters 88, 072104(2006) discloses a method of forming an InAs/GaSb multiple quantum well on a GaAs substrate by standard MOVPE. This document states that an InSb strain-compensating layer is the cause of formation of nanopipes and hence is not employed. Y. Huang, et al. “Epitaxial growth and characterization of InAs/GaSb and InAs/InAsSb type-II superlattices on GaSb substrates by metalorganic chemical vapor deposition for long wavelength infrared photodetectors”, Journal of Crystal Growth 314, 92 (2011) discloses a method of forming, on a GaSb substrate, an InAs/GaSb multiple quantum well including a strain-compensating layer (layer constituted by combination of InAsSb and InGaSb) by standard MOVPE. Li-Gong Li, et al. “Effect of growth temperature on surface morphology and structure of InAs/GaSb superlattices grown by metalorganic chemical vapor deposition”, Journal of Crystal Growth 359, 55 (2012) discloses a method of forming, on a GaSb substrate, an InAs/GaSb multiple quantum well including an AsSb-mixing-plane serving as a strain-compensating layer by standard MOVPE. H. J. Haugan, et al. “Exploring optimum growth for high quality InAs/GaSb type-II superlattices”, Journal of Crystal Growth 261, 471 (2004) discloses an example of forming, on a GaSb substrate, an InAs/GaSb multiple quantum well including an InSb strain-compensating layer by MBE.